This invention relates generally to cooling systems and, more particularly, to a system of cooling a plurality of containers such as food coolers or freezers.
It is known in the art to utilize cool outside air to supplement or replace refrigerated air provided to cases and freezers inside of buildings. Examples of the prior art techniques for accomplishing this are found in U.S. Pats. Nos. 1,053,443 issued Feb. 18, 1913; 2,067,9559 issued Jan. 19, 1937; 4,023,947 issued May 17, 1977; and 4,147,038 issued Apr. 3, 1979.
All of the prior art devices, to the knowledge of the present applicants, operate on the principal of sensing the ambient temperature and when the ambient air falls below a predetermined temperature value, an auxiliary cooling unit drawing cold outside air operates to maintain the temperature inside the refrigerated container at a temperature below the temperature setting for the thermostatically controlled primary refrigeration unit. In this manner, the primary unit remains inactive during an interval of time when outside temperature is below the predetermined temperature value.
The primary disadvantage of the prior art systems is that they offer no "transition phase" between cooling with the primary refrigeration units and cooling with outside air. This limits the use of the systems to environments where outside air temperature is very cold for long periods of time. These systems also require that the temperature at which outside air is utilized be several degrees below the desired temperature of the area being cooled so as not to experience excessive shifting between the primary and auxiliary cooling systems which would detract from the operating efficiencies.
It is, therefore, a primary object of the present invention to provide a cooling system for a plurality of cooling units which increases the energy efficiency required for cooling by utilizing a single mechanical cooling means to provide cool air for all of the units when the environmental temperature drops below a predetemined value which value is above the temperature at which outside air may be efficiently utilized.
It is also an objective of the present invention to provide an improved cooling system for multiple cooling units located inside of a building which provides for an auxiliary cooling unit to cool all containers when a first temperature drop is experienced and then utilize outside air for cooling of the units when a second temperature drop is experienced.
It is also an important aim of the invention to provide auxiliary cooling means for a number of refrigerated containers, which auxiliary cooling means is operated in response to an environmental temperature drop and wherein the auxiliary unit may have one or more components in common with one of the primary refrigeration units.
A further objective of the invention is to provide a cooling system as described above which includes a failsafe circuit so that in the event of an unexpected temperature rise the conventional refrigeration units will be reactivated.